TACKY POLYURETHANE COMPOSITES

Abstract

A number of tacky polyurethane or other gel comprising composites are provided. The composites have foam carriers, which may be open cell, semi-open cell, reticulated or closed-cell foam. The tacky gel which, in one embodiment, may be polyurethane, typically comprising a thin surface coating on the foam gel and the foam is partially or fully saturated with the same gel comprising the thin surface layer of the foam. The skeletons may be included in the composite to provide additional structure integrity, and a moisture proof layer may be added to the top and/or bottom surfaces of the foam/gel.

Claims

1. An assembly for use with an aircraft body, the assembly comprising: a removable workpiece having a workpiece surface; a static base having a base surface; a gasket for placement between the removable workpiece and the static base, the gasket comprising a cured, sticky, elastomeric polyurethane at least partially saturating a compressible foam body having an upper surface and a lower surface; and a dimensionally stable skin on one of the upper surface or the lower surface of the body, the skin forming a first gasket surface, the other of the upper surface or lower surface forming a second gasket surface, the second gasket surface having a thin, tacky layer of the cured polyurethane thereon in an uncompressed state; wherein the gasket, under compression between the workpiece and the base, allows some movement of the cured, polyurethane through the body but not the skin; wherein the second gasket surface non-adhesively and removably contacts the static base when under compression and the first gasket surface removably contacts the workpiece surface when under compression and removably releases from the workpiece surface; wherein the tack between the static surface and the gasket is greater than the tack between the gasket and the workpiece surface; and fasteners for compressing the gasket between the removable workpiece surface and the base surface.

2. The assembly of claim 1 further comprising a skeleton.

3. The assembly of claim 2 wherein the skeleton is metallic.

4. The assembly of claim 2 wherein the skeleton is non-metallic.

5. The assembly of claim 2 wherein the skeleton is woven.

6. The assembly of claim 1 wherein the foam is reticulated foam.

7. The assembly of claim 1 wherein the foam if open cell foam.

8. The assembly of claim 1 wherein the polyurethane is a gel.

9. The assembly of claim 7 wherein the polyurethane gel has a hardness of between 40 and 150 35 gram half cone penetrometer.

10. The assembly of claim 2 wherein the skeleton is a non-woven nylon web.

11. The assembly of claim 1 wherein the gel includes multiple small electrically conductive particles.

12. The assembly of claim 1 wherein the gasket is between about 30 and 500 mil thick uncompressed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIGS. 1, 2, and 3 illustrate exploded cross-sectional views of various embodiments of Applicant's novel gasket/tape

[0021] FIGS. 1A, 2A, and 3A all illustrate cross-sectional views of Applicant's assembled gasket tape, showing at least some of the ingress of the polyurethane gel onto and at least partially into the foam body of the carrier.

[0022] FIGS. 4 and 4A are views of another alternate embodiment of Applicant's invention.

[0023] FIGS. 5, 5A, and 5B are views of another alternate embodiment of Applicant's invention.

[0024] FIGS. 6 and 6A are views of a floorboard/stringer assembly that may use one or more embodiments of Applicant's tacky polyurethane composites

[0025] FIG. 7 is an elevational view of a composite in tape form.

[0026] FIG. 8 is an illustration of a flexible reticulated foam.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0027] FIG. 1 illustrates a composite structure 20 which may be used as a gasket, tape or sealant, which may be comprised of either an open 10, semi-open 11, closed 12 or reticulated 13 foam carrier, such as, in one embodiment, polypropylene or polyurethane foam. In one embodiment, a sticky or tacky cured polyurethane gel top layer 16, and a similar bottom layer 18 is provided in a manner that may either partially or completely saturate the foam and/or adhere to the surface of the closed cell foam. In one embodiment, a PTFE sheet 17, which is fluid and moisture proof, is adhered to the top and/or bottom foam layer, so it adheres to the gel, but presents a non-sticky, slideable moisture proof surface to the workpiece or base. This provides ease of positioning the workpiece when the gasket is in place.

[0028] FIG. 1A and the Detail illustrate in a compressed state that the use of foam, such as allows at least some of the gel to soak through and into any open cells of the foam. Even with closed cell foam, there is typically some migration of polyurethane gel into the foam under compression between a workpiece and a base or another workpiece.

[0029] FIG. 2 illustrates another composite structure 22, in which a pair of partly or fully gel soaked foam carriers, typically polypropylene or polyurethane foam, are used with a sticky or tacky gel middle layer 24 of cured elastomeric polyurethane gel, along with a top 16 and bottom 18 layer. This additional gel may provide additional resiliency to the composition and help the foam layers to adhere to one another. A PTFE or other suitable film 17 may be provided on the outer surfaces of either of the gel layers 16/18.

[0030] Foam carriers 10/11/12/13 act to provide some dimensional stability, even though, in some embodiments, they may allow stretch, indeed up to over 500%. They also act as a base for the tacky polyurethane gel for absorption there into. PTFE film or other suitable material may be used on either the top or bottom of the gaskets as a moisture barrier and to provide a non-tacky, slick surface for engaging a workpiece or base.

[0031] FIG. 2A represents composite structure 22 in a compressed state. such as between an aircraft base and an aircraft workpiece. As in FIG. 1A, it may be seen that the foam layers or carriers may at least partially absorb some of the polyurethane gel. The use of the foam carrier may provide some resiliency to the composite as well as some dimensional stability to the composite. The use of more than one foam, such as both an open cell and a closed cell carrier layer may provide additional resiliency.

[0032] FIG. 3 illustrates a composite 28 that includes a skeletal member 24, which in one embodiment is woven, such as a metallic or non-metallic fabric. On both sides of the skeletal member 24, foam carriers 10/11/12/13 may be provided. A gel layer 16/18 may be interposed between the foam or on the outside of both foam members (see FIG. 3) or both. In one embodiment, two open cell foam layers “sandwich” polyurethane gel layers, with no polyurethane gel on the outside of surfaces of the two foam carriers. In another embodiment, polyurethane coats one or both of the outer surfaces of the foam carrier also.

[0033] FIG. 3A shows composite 28 under compression wherein in the manufacturing or compression process an open cell polypropylene or other suitable foam has absorbed at least some of the polyurethane gel and the polyurethane gel has worked through the weaves of a skeletal fabric, such that the entire composite 28 is saturated or substantially saturated with the gel.

[0034] A sticky, soft polyurethane gel may be the gel disclosed in U.S. Pat. Nos. 6,530,577; 6,695,320; and 7,229,516, which patents are incorporated herein by reference and US Publication 2004/0041356, which is incorporated herein by reference. The composite structures may be made according to the teachings set forth in US Publication Nos. 2004/0070156 and 2004/0041356, incorporated herein by reference.

[0035] Gaskets of the composite may be made as by die cutting as set forth in US Publication Nos. 2004/0070156 and 2004/0041356, and U.S. Pat. Nos. 6,530,577; 6,695,320; and 7,229,516. The foam may be; in one case, open or closed cell polypropylene foam, in the range of about 30 to 250 mil thick. The composite structures formed may have a pre-compression thickness in the range of about 30 to 500 mil, and a compressed thickness of about 10 to 450 mil when under about 50 to 500 psi.

[0036] The uses of the composite structures illustrated may be for aircraft gaskets or sealant tape. They may be used underneath the floorboards, underneath laboratories, in stringers, sealing access panels, on antennae and in galleys to help prevent against corrosion. Optional skin 17 is shown to be, in one embodiment, a PTFE sheet acting as a moisture barrier and providing substantial dimensional stability. It may be any suitable moisture proof sheet that sticks to the polyurethane and contacts the workpiece. It may be used on one side, both sides or it may be omitted entirely. Skeleton 24 may be metallic or non-metallic, may be fiberglass, may be woven or unwoven and, in one embodiment, with a weave density of approximately 20 to 80.

[0037] The polyurethane may be the polyurethane as described in the patents and publications incorporated herein by reference. It may be a two component cured polyurethane, which contains no silicon, and is used in a tape or gasket. Unlike pressure sensitive adhesive layers, polyurethane provides a tackiness and retentivity and provides both a good environmental seal as well as ease of removal and reuse.

[0038] One method of making an embodiment of a foam composite structure may be found in US Publication No. 2005/0109190 entitled Dampening Material For A Drum. This publication is incorporated herein by reference. While the reference discloses an open cell foam, a closed cell foam may be partially saturated with a pre-cured polyurethane mix as set forth in the published application and then allowed to cure. Closed cell foam may be used with the uncured mix, which will typically penetrate at least those cells of the closed cell foam that are open to the surface of the foam carrier. Moreover, when the closed cell foam is subject to compression as when a workpiece is tightened down to a base with a gasket having closed cell foam and gel coated structure therebetween, some of the cells of the foam may break and the gel, though cured, is deformable and flowable under compression and may be forced into such broken cells, Thus, even closed cell foam may have some penetration of the gel thereinto

[0039] In an alternate embodiment of any of the composites, skin 17 is not PTFE, but is a woven fabric, metallic or non-metallic, with sufficient open pore space to allow some of the gel to seep through under compression, typically between about 100 and 500 psi. This results in a “semi-tacky” surface and easy removal of the one piece base, but still provides for a good environmental seal against the workpiece or a base due to its ability to allow the tacky gel to seep through the material and reach the surface of the workpiece and base and fill surface irregularities and the like.

[0040] Applicant's pre-cured polyurethane elastomer sealant with the polypropylene foam carrier may also be used in tape form for sealing and moisture proofing around mated electrical connectors, coaxial connectors, circumferential and irregular surfaces. While the open cell foam may be saturated or partly saturated, the closed cell foam may be coated with a polyurethane gel.

[0041] With a PTFE skin on one side, it can provide single sided sealing. Wth a semi-porous skin on one or either side, it can provide a semi-tacky gasket or tape sealant, One such fabric that will provide a semi-porous skin is a metallized woven fabric Zell-CR, from Shieldex Trading, Palmyra, N.Y.

[0042] FIGS. 4, 4A, 5, 5A, and 5B illustrate alternate preferred embodiments of Applicant's embodiments. FIGS. 4 exploded and 4A under compression illustrate the use of a specific type of skeleton 24, more specifically, a molded or extruded nylon web or any of the other skeletons disclosed in U.S. patent Ser. No. 14/484,570, filed Sep. 12, 2014, incorporated herein by reference. While Applicant is illustrating in FIGS. 4, 4A, 5, 5A, and 5B, the use of the specific skeleton in the form of web 24, it is to be understood that any of the other embodiments of the invention set forth herein may have this skeleton, for example, the embodiments illustrated in FIGS. 3 and 3A. Indeed, the skeletons of any embodiment may be metallic, non-metallic, woven, non-woven, rigid metal foam, molded or extruded nylon or plastic, web or any other material that is comprised of a non-foam material that will provide some dimensional and structural integrity to the foam/gel and other elements of the composites while being capable of retaining, in voids or openings therein, a gel or other suitable matrix.

[0043] In FIGS. 4 and 4A, a tacky composite 32 is illustrated. The skeletal web typically, when the product is manufactured and in use, carries a thin layer of gel on the upper surface thereof, and gel therethrough in the voids of the skeleton 24 and, if a FIFE or skin-type sheet is used (as shown optional, without), then stickiness to the lower or bottom surface of the gasket may be provided by foam 10111/12/13, which may comprise a type foam, which may be partially or fully saturated with gel or other suitable tacky matrix. Typically, a thin, sticky lower layer of gel 18 is present on the finished product 32.

[0044] FIGS. 5 and 5A illustrate an alternate preferred embodiment 34, which comprises Applicant's novel molded or extruded nylon or plastic web 24 as seen in the '570 application, with a foam/gel on the top and the bottom thereof. Foam 10/11/12/13 may be opened, closed, reticulated or semi-opened, and may be partly or fully saturated with the gel to provide tackiness on either side of the composite 34.

[0045] As stated above, the foam may be any flexible, compressible foam of an opened, closed or semi-opened cell foam (see, for example, U.S. Pat. No. 8,561,310, incorporated herein by reference for a semi-opened nylon foam). Any of the composites disclosed may have a PTFE skin on the upper, lower or both surfaces or in between. Using the skin, of which PTFE is one example thereof, will present a substantially non-tacky surface to the workpiece. In some applications, it may be preferable for the composite to have a tacky side, with a tacky gel on the surface of a foam or on the surface of a skeleton, such as seen in FIG. 4, for exposure to and contact with the workpiece under compression to provide a good environmental seal.

[0046] Other types of foam are those disclosed in Application US 2013/0224434, which disclose using an open cell foam with pressure sensitive adhesives other than a gel for stickiness.

[0047] Applicant's gel may be a polyurea gel, polyurethane gel or other suitable two-part polymer gel. It may have a peel strength of about 0.3 and 1.0 lb./in. width, or about 0.1 and 2.0 lb./in. width. Gel soaked open cell foam with a PTFE liner (AVDEC HT-3000) and another with a 2 mil polyfilm (AVDEC AD-89513) yielded a range of 65-85 Shore “00” or 35 to 65 Shore “A”. this range is appropriate for Applicant's composites, also a broader range 50-100 on Shore “00”, 25-75 on Shore “A”. The gel can be two-part mix chemically cured as seen, for example, in U.S. Pat. No. 7,229,516, incorporated herein by reference, or may be thermally or otherwise cured. The gel is typically impregnated into the foam in those composites which call for such partial/complete saturation, and the gel is uncured and the gel is allowed to cure in place.

[0048] In some embodiments, the gel may be infused with a carry and suspension conductive particles for providing some conductivity between workpieces, such as metal parts, providing compression to Applicant's composites. These particles may be graphene mixed in the gel or the resin and graphene mix as disclosed in U.S. Pat. No. 8,652,362, incorporated herein by reference, the metal pigments disclosed in US Publication No. 2013/0168612, incorporated herein by reference, the metal particles disclosed in the Parker-Hannifin U.S. Pat. No. 8,633,402, incorporated herein by reference, or any other suitable conductive or semi-conductive particle.

[0049] Both gaskets and tape are anticipated for the configurations of Applicant's composites disclosed herein. Some of these composites, that lack a skeleton or have a skeleton that is flexible may be suitable for a partially stretchable tape that may be used to wrap electrical conductors as found, for example, in U.S. Pat. No. 7,229,516, FIG. 1B, incorporated herein by reference. All composites can be with or without a skeletal member and with or without a moisture proof barrier.

[0050] Another embodiment for Applicant's composite 38 (FIG. 5B) may be between floorboards FB of an aircraft and support stringers S or members (see FIG. 6). In this particular embodiment 38 (FIG. 5B), a “skinned” version of Applicant's tacky composite may be used with the tacky side on the aircraft structure and the impermeable or partially porous skin against the surface of the floorboard for ease of positioning the floorboard and ease of removability.

[0051] FIGS. 6 and 6A illustrate the use of any of Applicant's composites herein designated “C” in a particular embodiment, namely, between the floorboards FB and stringers S of an aircraft. Typically stringers S have multiple holes H therein and floorboards FB are fastened down to the stringers S with a gasket or tape material therebetween to help avoid corrosion and the spread of moisture. In one embodiment, a tape 35 comprising a linear strip of composite C is provided, which tape 35 may include release film 36 on a surface thereof and may, in one embodiment be a composite C with a skin on an upper surface thereof. That is, composite C may be placed, sticky side down, onto stringers S and skin 17 on an upper side of the composite will allow easy movement of floorboard FB to align holes Hin the floorboards with holes Hin the stringers and the application of fasteners F therethrough. A piercing member P may be used after the floorboards are in place to pierce through composite C to allow fasteners F to pass therethrough following removal of piercing member P

[0052] Ease of removability may be achieved by using a skeleton of a harder nature, for example, Applicant's molded or extruded nylon skeleton instead of woven fiberglass or a non-woven skeleton is more resistant to compression. Ease of removability may also be achieved by using a thicker skeleton, for example, a skeleton in the range of 18 to 28 mil, rather than, for example, in the range of 8 to 17 mil. The foam under compression may tend to impeded somewhat the lateral movement of gel with less edge squeeze out than cured gel.

[0053] FIG. 8 illustrates a reticulated flexible foam for use in any of Applicant's tacky composites. Reticulated foam is a very porous, low density solid foam. “Reticulated” means like a net. Reticulated foams are extremely open foams and few, if any, contain cell windows. A reticulated foam may be made of an organic binder, like polyurethane, and be flexible. They have a high porosity and a large surface area. Porosity may be over 90%, sometimes 95%, or as high as 98%. Reticulated foams are sometimes used in scrubbers or air conditioner filters. Any of Applicant's tacky embodiments may use reticulated foam carrier 13 and, in one case, a reticulated foam provided by Riley Foam Corporation as the SIF® filter foam for air filter applications. This is a polyester urethane foam with a three-dimensional structure of skeletal strands. Each cell in the foam is completely interconnected with all surrounding cells. It has a high tensile strength and tear resistance together with easy workability. This filter foam is produced in a number of pore sizes, expressed as the average number of pores per linear inch, and may run from about 5 to about 100 ppi. It can withstand intermittent temperatures as high as about 250° F. and has a void volume of about 97%. It is not adversely affected by water, detergents or else solvents or grease at normal operating temperatures. Tensile strength ranges between about 22 to about 35 psi, and elongation between about 275% to about 400%. Nominal pore size may be variable for a given thickness and, in one embodiment, may be between 40 and 110 and a porosity grade between 45 and 100.

[0054] FIGS. 5A and 5B illustrate embodiment 38 with a foam gel layer 10/11/12/13, which may be manufactured according to the AVDEC patents incorporated by reference. Also, a nylon web or skeleton 24 is placed adjacent a surface of the saturated foam gel before the material is compressed between two parts. The nylon web may be partially or fully saturated before placement adjacent the foam gel, before placement between the aircraft parts or the nylon web may be dry and compression when the aircraft parts are torqued down will force the gel from the foam gel to migrate into the open spaces of the nylon web and adjacent the face of the workpiece adjacent the nylon web, effectively coating it to provide environmental seal.

[0055] FIGS. 1, 2, 3, and 4 show gel layers separate from the foam for illustration, but it is to be understood that unless the foam is a closed cell foam, the open, semi-open or reticulated foam is saturated prior to use by the methods set forth in the AVDEC patents. When open cell foam is used, the gel may be layered separately, alternating with the closed cell foam in the methods described in the patents.

[0056] When non-closed cell foams are used in the manufacturing process as set forth in the patents that are incorporated by reference, it is to be understand that in all of the compositions, gel tends to migrate when the compositions are placed between workpieces which are then placed under compression, for example, by fasteners. The gel will tend to migrate between openings in any type of a skeletal member, openings in the open cells of the foam, including closed cellfoam where the cells have been broken by virtue of compression, and typically vertical migration stopped only by impervious skin/barrier, such as RIFE 17. That is to say, the composites, excepting the skin, are typically encapsulated with gel, the gel providing a good environmental seal, the foam providing some resiliency and some (though usually not total) resistance to migration as well as some structural stability and the skeleton, if present, providing additional stability,

[0057] Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention.